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366 SSSAJ: Volume 74: Number 2 • March–April 2010
Soil Sci. Soc. Am. J. 74:366–371
Published online 8 Jan. 2010
doi:10.2136/sssaj2009.0075
Received 24 Feb. 2009.
*Corresponding author (Yaling.Qian@colostate.edu).
© Soil Science Society of America, 677 S. Segoe Rd., Madison WI 53711 USA
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by
any means, electronic or mechanical, including photocopying, recording, or any information storage
and retrieval system, without permission in writing from the publisher. Permission for printing and for
reprinting the material contained herein has been obtained by the publisher.
Soil Organic Carbon Input from
Urban Turfgrasses
Soil Carbon Sequestration & Greenhouse Gas Mitigation
Carbon sequestration is the process of capturing and storing C in organic form
in soil organic matter. Experts believe that soil C sequestration will reduce
the buildup of CO2 (a greenhouse gas) in the atmosphere while improving the
nation’s soil, air, and water quality and the agricultural economy (Lal and Follett,
2009). Intensive research has been conducted to quantify C sequestration in agri-
cultural lands; however, research to quantify the C sequestration potential of turf-
grass systems is very limited. Previously, we conducted an initial study to assess soil
C sequestration in golf course fairways and putting greens using historic soil testing
data in Colorado and Wyoming (Qian and Follett, 2002). We found that a rapid
SOC accumulation occurred during the rst 25 yr a er turfgrass establishment,
at average rates approaching 0.9 and 1.0 Mg C ha−1 yr−1. ese rates are com-
parable to those reported for U.S. land that has been placed in the Conservation
Reserve Program (Follett et al., 2001). ese results suggest that turfgrass is e ec-
tive in sequestering atmospheric CO2 and in improving soil quality. Considering
that turfgrass acreage is three times larger than any irrigated crop, covering more than
16 million ha in the continental United States (Milesi et al., 2005), further research is
needed to quantify C sequestration of turfgrasses under di erent management regimes.
Management of turfgrasses is highly variable, in part because of the di er-
ent uses, species, nutrient inputs, and management levels. Milesi et al. (2005) es-
timated the potential C ux in turfgrass systems using the Biome-BGC ecosys-
tem process model and assuming that the entire turf surface across 48 states was
managed homogeneously. Golubiewski (2006) found, however, that management
Yaling Qian*
Dep. of Horticulture and Landscape
Architecture
Colorado State Univ.
Fort Collins, CO 80523-1173
Ronald F. Follett
USDA-ARS
Soil–Plant–Nutrient Research Unit
Fort Collins, CO 80522
John M. Kimble
USDA-NRCS (retired)
151 East Hill Church Road
Addison, NY 14801
Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species
selection, irrigation, and mowing may a ect C input and storage in these systems. Research was conducted to
determine the rate of soil organic C (SOC) changes, soil C sequestration, and SOC decomposition of ne fescue
(Festuca spp.) (rainfed and irrigated), Kentucky bluegrass (Poa pratensis L.) (irrigated), and creeping bentgrass
(Agrostis palustris Huds.) (irrigated) using C isotope techniques. We found that 4 yr a er establishment, about
17 to 24% of SOC at 0 to 10 cm and 1 to 13% from 10 to 20 cm was derived from turfgrass. Irrigated ne fescue
added the most SOC (3.35 Mg C ha−1 yr−1) to the 0- to 20-cm soil pro le but also had the highest rate of SOC
decomposition (2.61 Mg C ha−1 yr−1). e corresponding additions and decomposition rates for unirrigated ne
fescue, Kentucky bluegrass, and creeping bentgrass in the top 20-cm soil pro le were 1.39 and 0.87, 2.05 and
1.73, and 2.28 and 1.50 Mg C ha−1 yr−1, respectively. Irrigation increased both SOC input and decomposition.
We found that all turfgrasses exhibited signi cant C sequestration (0.32–0.78 Mg ha−1 yr−1) during the rst 4 yr
a er turf establishment. e net C sequestration rate was higher, however, for irrigated ne fescue and creeping
bentgrass than for Kentucky bluegrass. To evaluate total C balance, additional work is needed to evaluate the total
C budget and uxes of the other greenhouse gases in turfgrass systems.
Abbreviations : SOC, soil organic carbon ; SON, soil organic nitrogen; δ13C, carbon isotope ratio.
SSSAJ: Volume 74: Number 2 • March–April 2010 367
level dominates the response of turfgrass production and tissue
N concentration, which, in turn, in uences the amount of C and
N both stored in and harvested from the turf site. Research to
document the e ects of di erent management scenarios on soil
organic C and N changes will aid in a better understanding of
the impact of turfgrass on urban ecosystem C budgets.
Approximately 1.1% of the C in the biosphere is in the
form of the stable isotope 13C and 98.9% as the stable isotope
12C. e photosynthetic pathways of cool- and warm-season
plants discriminate 13C di erently, thus resulting in di erent
C isotope ratios (13C/12C), expressed as δ13C and having per
mil (‰) units. e sign of the δ13C value indicates whether the
sample has a higher or lower 13C/12C isotope ratio than Pee
Dee belemnite (PDB), a limestone standard from near Pee Dee,
SC (Boutton, 1991). e mean δ13C of warm-season and cool-
season plant tissues are near −27 and −13‰, respectively (Clay
et al., 2006; Deines, 1980; Follett et al., 2004). erefore, the
abundance of the natural 13C or δ13C may aid in partitioning
SOC with regard to its origin. For example, when cool-season
turfgrass is established on previous warm-season (such as corn
[Zea mays L.]) elds or warm–cool-season rotation elds (such
as corn–soybean [Glycine max (L.) Merr.] rotations), isotope
techniques can be e ectively used to trace how fast turfgrass
can contribute to the SOC accumulation. is technique has
been successfully used in agricultural and native grasslands to
assess soil C sequestration. By using a C isotope methodology,
Gregorich et al. (1995) was able to determine that, following 25
yr of continuously grown corn on a forest soil in eastern Ontario,
about 30% of the SOC in the plow layer (0–27 cm) was derived
from the corn. Gregorich et al. (1996) also used 13C abundance
methods to account for the higher amount of C4 plant-derived
C in long-term N-fertilized soils compared with unfertilized
soils. Follett et al. (1997) had also earlier used 13C abundance
methods to determine the e ciency of incorporation of small-
grain crop residue into soils with a native warm-season grass
origin in the Great Plains. Follett et al. (2009) recently used 13C
abundance methods to determine that the conversion of a eld
that had been in 13 yr of continuous smooth bromegrass to no-
till corn production did not result in any net change in SOC dur-
ing a 6-yr corn production period in the western U.S. Corn Belt;
however, there was a signi cant change in the relative amount
of SOC that remained from the C3 bromegrass and the amount
added by the C4 corn during the 6 yr, and a redistribution of
SOC into di erent soil aggregate size classes.
e main objectives of this study were to: (i) determine the
amount of SOC derived from turfgrass a er 4 yr of establish-
ment on a previous corn and soybean (as rotation crops) eld
using the C isotope technique; and (ii) determine soil C seques-
tration and organic C decomposition from di erent turfgrasses.
MATERIALS AND METHODS
Experimental Site and Management
e selected research site was located on Arbor Links Golf Course,
Nebraska City, NE. e study site was originally a native prairie occu-
pied by a mix of warm- and cool-season plants (Krings and Kimble, per-
sonal communication, 2008). In the 1860s, native plants were cleared
to grow wheat (Triticum aestivum L.), oat (Avena sativa L.), sorghum
[Sorghum bicolor (L.) Moench], and corn as rotation crops. e crop-
ping sequence changed to a corn–soybean rotation in the 1970s. In
2000, the ground in this area was reshaped for golf course development.
Based on the weather station record (weather station no. 255810, High
Plains Regional Climate Center), the average annual precipitation rate
of the study site is approximately 86 cm, with an average high tempera-
ture ranging from 0°C in January to 31°C in July and an average low
temperature ranging from −21°C in January to 19°C in July. e soil
of the study site is an Aksarben silty clay loam (a ne, smectitic, mesic
Typic Argiudoll) with an average pH of 6.8.
In the fall of 2001, the following turfgrasses were seeded in rep-
licated plots: unirrigated ne fescue (a mixture of hard fescue [Festuca
brevipila R. Tracey) and sheep fescue [Festuca ovina L.]), irrigated ne
fescue (a mixture of hard fescue and sheep fescue), Kentucky bluegrass
(a blend of ‘Moonlight,’ ‘Award,’ and ‘Brilliant’), and creeping bentgrass
(‘Seaside II’). Seeding rates were 35, 74, and 196 kg ha−1 for creeping
bentgrass, Kentucky bluegrass, and ne fescue, respectively. A er seed-
ing, the experimental area was irrigated lightly three times daily until
3 wk a er seeding. erea er, the plots were irrigated as needed to pre-
vent drought and encourage establishment for the remaining season of
the establishment year.
During growing seasons from 2002 to 2005, di erent manage-
ment regimes were applied to re ect four management intensities.
Brie y, creeping bentgrass plots were managed as fairway turf: mowed
every other day to 1.5 cm and irrigated every other day at about 90 to
100% evapotranspiration (ET). Kentucky bluegrass plots were man-
aged as short rough: mowed twice a week to 3.8 cm and irrigated twice
a week at 90 to 100% ET. Irrigated ne fescue plots were managed as
rough: mowed to 5.1 cm weekly and irrigated twice a week at 70% ET.
Rainfed ne fescue plots were managed as unirrigated rough: mowed
to 5.1 cm when necessary. All plots were fertilized with 150 kg ha−1
N annually from 2002 to 2005. During mowing events, clippings were
returning to the soil.
Sample Collection, Measurement, and Analysis
In November 2001 (2 mo a er seeding), November 2002 (1 yr
a er turf establishment), and October 2005 (4 yr a er turfgrass estab-
lishment), the soil was sampled by rst removing the plant material
from the soil surface and then, using a at-bladed shovel, undercutting
and removing the soil from the 0- to 10- and 10- to 20-cm depths
as described by Follett et al. (2009). Soil bulk densities (at 33 kPa of
moisture tension) were determined on clods from each soil layer and
coated with Saran F-310 (Dow Chemical, Midland, MI) for transport
and measurement of soil bulk density (Burt, 2004). ree subsamples
from each plot at each depth were collected. Samples were analyzed
for total SOC, total soil organic N (SON), and δ13C. Root density
was also determined in 2001 and 2005. In addition, aboveground tis-
sues (shoots) were collected in 2005 from 100 cm2 of each plot for
determination of the plant tissue δ13C. To determine the root density,
de ned as root mass per unit mass of soil, soil samples were weighed
to determine fresh and dry mass. Roots were washed free of soil using
368 SSSAJ: Volume 74: Number 2 • March–April 2010
a hydro-pneumatic elutriation system, dried at 75°C for 2 d,
and the root mass was determined.
For determination of SOC and SON, roots (>1 mm in
length) were removed by hand before any analysis. All samples
of soil, roots, and shoots were analyzed for total C, total N, and
δ13C using a Europa Scienti c 20-20 Stable Isotope Analyzer
(isotope ratio mass spectrometer) continuous ow interfaced
with a Europa Scienti c ANCA-NT system (automated CN
analyzer) Solid/Liquid Preparation Module (Dumas com-
bustion sample preparation system) (Sercon Ltd., Europa
Scienti c, Crewe, UK).
Carbon Sequestration and Turfgrass Soil Organic
Carbon Contribution Calculations
The proportion of C derived from turfgrass, X%, at 4 yr after
the establishment of the turf, was calculated by the following equa-
tion. The equation is modified from Gregorich et al. (1996) and
Follett et al. (1997):
13 13
turf soil 2005 baseline
13 13
turf tissue baseline
CC
% 100
CC
Xδδ
δδ
−
=
−
[1]
where δ13Cturf soil 2005 is the δ13C of the soil samples collected in
2005, δ13C baseline is the δ13C of soil samples collected in 2001, and
δ13Cturf tissue is the combined δ13C of roots and shoots.
Carbon input from turfgrass during the specific period was
calculated as
2005
Gross SOC input from turfgrass SOC %X=
[2]
Changes in SOC content at establishment and 4 yr a er establishment
provided the C sequestration rate for the 4 yr following establishment:
2005 2001
Net C sequestration SOC SOC=−
[3]
By subtracting the net C sequestration from the gross C input, we de-
rived the soil C decomposition data.
RESULTS AND DISCUSSION
Vegetation Biomass
Aboveground vegetation biomass was determined only in
2005 (Table 1). For the irrigated ne fescue, Kentucky bluegrass,
and creeping bentgrass, a layer of thatch existed (thatch is a layer
of aboveground living and decaying plant material that forms be-
tween the soil surface and the green vegetation). erefore, the
aboveground tissue was separated into thatch and shoots
for biomass determination. Fine fescue, Kentucky blue-
grass, and creeping bentgrass allocated approximately
60 to 64% of the aboveground biomass in the form of
thatch. atch was not apparent, however, for the unir-
rigated ne fescue plots, so all the aboveground biomass
was grouped as shoots. Despite the di erence of thatch
biomass and mowing height, all grasses produced a simi-
lar amount of total aboveground biomass (Table 1).
Root Mass
One year a er establishment (2002), the unirrigated ne
fescue had a lower root density than the creeping bentgrass and
irrigated ne fescue at 0 to 10 and 10 to 20 cm, respectively
(Table 2). At the 0- to 10-cm depth, the creeping bentgrass ex-
hibited 1.6 times more roots than the unirrigated ne fescue.
At 10 to 20 cm, the irrigated ne fescue exhibited 140% more
roots than the unirrigated ne fescue. e root density of the
Kentucky bluegrass and creeping bentgrass was not di erent
from either unirrigated or irrigated ne fescue.
Four years a er establishment (in 2005), the ne fescue
(both irrigated and unirrigated) had a greater root density than
the Kentucky bluegrass and creeping bentgrass at both 0 to 10
and 10 to 20 cm (Table 2). Root production is probably related
to mowing height and species genetic potential. Fescues are gen-
erally believed to have deeper and more extensive root systems
than Kentucky bluegrass or creeping bentgrass.
Carbon Isotope Ratios
e mean δ13C values for the irrigated Kentucky bluegrass,
ne fescue, and creeping bentgrass shoots collected in October
2005 were −26.8, −26.2, and −27.3‰, respectively (Table 3). e
mean δ13C values of the roots were slightly higher than those of
the shoots (Table 3). Compared with the irrigated ne fescue, the
rainfed ne fescue had a less negative δ13C, with mean δ13C values
of −25.2 and −24.5‰ for its shoots and roots, respectively (Table
3). is di erence re ected the greater stomatal resistance caused
by lower water availability in the rainfed ne fescue.
We collected soil baseline samples in November 2001. e
baseline SOC δ13C was approximately −18.0‰, re ecting the
historical vegetation, i.e., a mix of C3 and C4 vegetation for the
land use history. e large distinguishable di erences in isotope
Table 1. Aboveground vegetation biomass of different grasses grown in
the eld under different management regimes.
Grass Mowing
height
2005 vegetation biomass
Shoots Thatch Total aboveground biomass
cm ———————— kg m−2 ————————
Fine fescue (unirrigated) 7.6 3.45 a† N/A 3.45
Fine fescue (irrigated) 5.1 1.17 b 1.83 3.01
Kentucky bluegrass 2.5 1.25 b 2.24 3.49
Creeping bentgrass 1.2 1.31 b 1.93 3.24
† Means followed by different letters are signi cantly different (P ≤ 0.05) by LSD.
Table 2. Root density of different grasses grown in the eld under differ-
ent management regimes.
Grass Mowing
height
2002 2005
Root density Root density
0–10 cm 10–20 cm 0–10 cm 10–20 cm
cm —————— g kg−1 dry soil ————
Fine fescue (unirrigated) 5.1 3.4 b† 0.38 b 36.3 a 10.4 a
Fine fescue (irrigated) 5.1 6.67 ab 1.25 a 33.9 a 10.2 a
Kentucky bluegrass 2.5 5.69 ab 0.70 ab 16.5 b 6.1 ab
Creeping bentgrass 1.2 8.42 a 0.88 ab 13.5 b 2.9 b
† Means followed by different letters in a column are signi cantly different (P ≤
0.05) by LSD.
SSSAJ: Volume 74: Number 2 • March–April 2010 369
signatures of the current turfgrasses vs. the SOC isotope baseline
suggest that our experimental approach was feasible.
Data on C isotope composition, SOC, SON, and the SOC/
SON ratio for soil samples collected in 2002 and 2005 are pre-
sented in Table 4. During the rst year a er the establishment
of turf (2001–2002), SOC increased and SON stayed at simi-
lar levels, which resulted in an increased C/N ratio of the soil
organic matter. e increased soil organic matter C/N ratio
indicated that the newly established turf systems favored N im-
mobilization, justifying a higher N fertilization need compared
with long-established and mature turfgrass systems. From 2002
to 2005, there was a continued increase in SOC for the unirri-
gated ne fescue, Kentucky bluegrass, and creeping bentgrass at
0 to 10 cm. At 10 to 20 cm, the change in SOC was small in
magnitude. From 2002 to 2005, the unirrigated ne fescue and
creeping bentgrass exhibited increases in the C/N ratio at 0 to
10 cm, whereas the soil C/N ratio of the irrigated ne fescue and
Kentucky bluegrass showed no change. At 10 to 20 cm, the C/N
ratio was slightly reduced from 2002 to 2005. ese data sug-
gest that 2- to 5-yr-old turf systems favor C sequestration at the
surface (0–10 cm).
Organic Carbon Input from Turf, Carbon
Sequestration, and Carbon Decomposition
Using Eq. [1], the percentage of SOC derived from individ-
ual turfgrasses in 2005 was calculated for both the 0- to 10- and
10- to 20-cm depths (Table 5). ese data show that 4 yr a er
turfgrass establishment on a previous corn–soybean eld in the
north-central United States, about 17 to 24% of the SOC was
derived from the turfgrass at 0 to 10 cm. At the 10- to 20-cm
depth, we found striking di erences among the turfgrass species.
For shallow-rooted Kentucky bluegrass and creeping bentgrass,
only about 1 and 4% of the SOC was derived from the turfgrass
at 10 to 20 cm, whereas for the deep-rooted ne fescue, about 10
to 13% was derived from the turfgrass. Fisher et al. (1994) found
that deep-rooted grasses introduced into South American savan-
nas for agricultural purposes sequestered signi cant amounts of
organic C deep in the soil pro le. ey suggested that a substan-
tial amount of C, globally, could be locked up in such a manner.
When we combined the data from the two depths, about 10 to
18% of the SOC (0–20 cm) was derived from turfgrass.
Using the bulk density data collected in 2001, which sug-
gested that all plots had similar bulk densities (Table 4), gross
SOC inputs by turfgrass were calculated (Tables 5 and 6).
During the initial 4 yr a er establishment, irrigated ne fescue
had a gross input of 3.35 Mg C ha−1 yr−1 to the 0- to 20-cm soil
pro le, which is about 141% higher than the SOC input from
unirrigated ne fescue, and 55% higher than irrigated Kentucky
bluegrass or creeping bentgrass.
Soil organic C content di erences between 2005 and 2001
indicated that SOC at 0 to 20 cm in the soil pro le increased
0.75, 1.10, 0.45, and 1.14 g kg−1 soil for unirrigated fescue, irri-
gated fescue, Kentucky bluegrass, and creeping bentgrass, respec-
tively. Based on the bulk density data collected in 2001, these
SOC changes translate to C sequestration rates of 0.52, 0.74,
0.32, and 0.78 Mg C ha−1 yr−1 for unirrigated ne fescue, irri-
gated ne fescue, Kentucky bluegrass, and creeping bentgrass, re-
spectively. All turfgrasses exhibited signi cant C sequestration;
however, the net C sequestration rate in the 0- to 20-cm soil pro-
le was higher in the irrigated ne fescue and creeping bentgrass
plots. Kentucky bluegrass had the lowest C sequestration rate
among the tested species. e C sequestration rate for unirrigat-
ed ne fescue was intermediate but was not statistically di erent
from Kentucky bluegrass or irrigated ne fescue. e C seques-
tration potential is related not only to the productivity of roots,
Table 3. Plant tissue C isotope composition 4 yr after
establishment.
Grass C isotope ratio (δ13C)
Root Shoot
———————— ‰ ————————
Fine fescue (unirrigated) −24.5 a† −25.2 a
Fine fescue (irrigated) −25.5 b −26.2 b
Kentucky bluegrass −25.7 b −26.8 b
Creeping bentgrass −26.27 c −27.3 c
† Means followed by different letters in a column are signi cantly
different (P ≤ 0.05) by LSD.
Table 4. Plant tissue C isotope ratio (δ13C), soil organic C (SOC), soil organic N (SON), and soil C/N ratio at the establishment of
different grasses and 1 and 4 yr after turf establishment.
Grass
2001 baselines 2002 data 2005 data
Shoot δ13C Soil δ13CSOC SON C/N Bulk
density δ13CSOC SON C/N δ13CSOC SON C/N
—–––– ‰ –––— ––— g kg−1 —–– ‰ ––– g kg−1 ––– ‰ ––– g kg−1 –––
0–10 cm
Fine fescue (unirrigated) −27.91 a† −17.54 13.0 ab 1.25 b 10.5 1.30 −18.55 14.2 ab 1.38 ab 10.2 ab −18.84 a 14.9 1.34 10.98
Fine fescue (irrigated) −27.99 a −18.05 15.5 a 1.57 a 9.9 1.25 −18.52 15.9 a 1.47 a 10.8 a −19.9 ab 15.7 1.44 10.86
Kentucky bluegrass −29.08 b −18.14 14.3 ab 1.37 ab 10.3 1.35 −18.89 14.8 ab 1.38 ab 10.8 a −19.61 ab 15.7 1.35 10.9
Creeping bentgrass −28.66 ab −18.35 12.3 b 1.27 b 9.2 1.32 −19.17 12.4 b 1.20 b 10.0 b −20.07 b 14.3 1.34 10.32
10–20 cm
Fine fescue (unirrigated) −27.91 a −18.20 7.6 0.94 8.1 1.44 −18.79 NS 7.7 NS 0.87 NS 8.6 NS −18.85 ab 7.2 0.85 7.87
Fine fescue (irrigated) −27.99 a −18.42 8.0 1.15 6.6 1.42 −18.93 11.5 1.10 9.9 −19.38 b 10.0 1.03 8.98
Kentucky bluegrass −29.08 b −17.61 11.8 1.27 9.0 1.44 −18.60 11.0 1.07 10.1 −17.68 a 11.3 1.14 9.72
Creeping bentgrass −28.66 ab −17.77 9.8 1.17 7.7 1.42 −18.84 10.0 1.02 8.8 −18.14 ab 10.08 1.05 8.74
† Means followed by different letters in a column are signi cantly different (P ≤ 0.05) by LSD.
370 SSSAJ: Volume 74: Number 2 • March–April 2010
rhizomes, and shoots, but also to SOC decomposition or turn-
over rates. is range of C sequestration is in agreement with the
following reported studies. Bruce et al. (1999) estimated a gain of
0.6 Mg C ha−1 yr−1 for previously cultivated lands that had been
reseeded to grass. Post and Kwon (2000) compiled literature data
for soil C in areas where grasslands have been allowed to devel-
op on previously disturbed lands and reported that the average
rates of C accumulation during the early grassland establishment
were 0.33 Mg ha−1 yr−1. Qian and Follett (2002) reported a C
sequestration rate of 0.9 to 1.0 Mg ha−1 yr−1 for highly managed
turfgrass systems in Colorado and Wyoming. e management
regime of Qian and Follett (2002) was similar as the manage-
ment regimes of Kentucky bluegrass and creeping bentgrass in
this study. e lower C sequestration ability of Kentucky blue-
grass found in this study than that reported by Qian and Follett
(2002) may have been due to the warmer climate, a smaller day–
night temperature di erence, and higher annual precipitation
encountered at this study site. Bandaranayake et al. (2003) and
Wang et al. (2000) suggested that higher temperature accelerates
the decomposition of SOC only when soil moisture is adequate,
and inhibits decomposition when soil moisture becomes limited.
By subtracting net C sequestration from gross C input, we
derived soil C decomposition data (Table 6). e SOC decom-
position rates were 1.73 and 1.50 Mg ha−1 yr−1 for Kentucky
bluegrass and creeping bentgrass, respectively, which were higher
than for unirrigated ne fescue and lower than for irrigated ne
fescue. By comparing irrigated and unirrigated ne fescue plots,
we found that irrigation increased the net organic C input to the
0- to 20-cm soil pro le by 141%. At the same time, irrigation also
increased SOC decomposition by twofold.
CONCLUSIONS
Urban grassland covers >16 million ha in the United States,
and it is ubiquitous in the American urban landscape.
Milesi et al. (2005) estimated that among the total land
in the United States devoted to urban development, 39
to 54% is covered by turfgrass. Despite the large acreage
of turf, the role of turf in balancing the nation’s C budget
has largely been unexplored. Previously, we have reported
that C sequestration ability is intricately linked to the cy-
cling of soil nutrients, including N, P, K, and micronutri-
ents (Qian and Follett, 2002), and clipping management
(Qian et al., 2003). Di erent C sequestration rates were
observed under di erent treatments. Carbon sequestration rates
were 0.74, and 0.78 Mg ha−1 yr−1 for irrigated ne fescue and
creeping bentgrass, respectively, which are higher than those of
unirrigated ne fescue and irrigated Kentucky bluegrass. In this
experiment, we observed that irrigation increased both the gross
SOC input to the soil pro le and SOC decomposition in ne
fescue. us, the SOC accumulation rate is associated with both
turfgrass rooting depth and irrigation availability.
In summary, our experiment demonstrates that urban turf-
grass systems provide a signi cant sink for SOC sequestration.
Measurement of the C isotopic composition appears to be an
appropriate approach to study SOC dynamics. Soil C sequestra-
tion and organic C decomposition rates are di erent for di er-
ent turfgrasses and di erent management regimes.
To consider the net impact of urban grassland on the atmo-
sphere’s greenhouse e ect, however, we need to consider fuel ex-
penses in maintaining the turfgrass, fertilizer and pesticide use,
energy for pumping water to irrigate, and the uxes of other green-
house gases (mainly N2O and CH4) in addition to soil C seques-
tration. Additional work is needed to evaluate the total C budget
and uxes of the other greenhouse gases in turfgrass systems.
ACKNOWLEDGMENTS
We gratefully acknowledge the important contributions of Mr. Edward
Buenger and Ms. Elizabeth Pruessner in the Soil–Plant–Nutrient
Research Unit of the USDA-ARS, the important contributions of Ms.
Sarah Wilhelm in the Dep. of Horticulture and Landscape Architecture
at Colorado State University, the important assistance provided by the
National Soil Survey Laboratory of the NRCS, and eld assistance
and coordination with NRCS by Mr. Steve Scheinost, Assistant State
Soil Scientist for the NRCS in Nebraska. We are grateful to Mr. Ryan
Krings, the superintendent of Arbor Links Golf Course. is study is
partially supported by USDA-ARS funding to address the objectives
of the GRACEnet Cross Location Research project, by the Colorado
Agricultural Experiment Station, and by the International Turf
Producer’s Foundation.
Table 5. Percentage of soil organic C (SOC) from turf and C inputs from turfgrass at 0 to 10 and 10 to 20 cm in the soil pro le
under different turfgrasses in 2005.
Grass
0–10 cm 10–20 cm 0–20 cm
SOC
from turf Total SOC SOC
from turf
SOC
from turf Total SOC SOC
from turf
SOC
from turf
C input
from turf
% g kg−1 % g kg−1 % g kg−1
Fine fescue (unirrigated) 17.8 14.9 2.65 9.78 a† 7.2 0.70 13.8 2.03 b
Fine fescue (irrigated) 23.7 15.7 3.72 12.92 a 10.0 1.29 18.3 5.02 a
Kentucky bluegrass 18.2 15.7 2.85 0.81 b 11.3 0.09 9.5 2.94 ab
Creeping bentgrass 20.4 14.3 2.92 4.10 b 10.1 0.41 12.2 3.33 ab
† Means followed by different letters in a column are signi cantly different (P ≤ 0.05) by LSD.
Table 6. Gross soil organic C (SOC) input, net soil C sequestration, and SOC
decomposition in the 0- to 20-cm soil pro le under different turfgrasses.
Grass Gross SOC input
from turf
Net C
sequestration
SOC
decomposition
———————— Mg ha−1 yr−1 —————————
Fine fescue (unirrigated) 1.39 b† 0.52 ab 0.87 c
Fine fescue (irrigated) 3.35 a 0.74 a 2.61 a
Kentucky bluegrass 2.05 ab 0.32 b 1.73 b
Creeping bentgrass 2.28 ab 0.78 a 1.50 b
† Means followed by different letters are signi cantly different (P ≤ 0.05) by LSD.
SSSAJ: Volume 74: Number 2 • March–April 2010 371
REFERENCES
Bandaranayake, W., Y.L. Qian, W.J. Parton, D.S. Ojima, and R.F. Follett. 2003.
Estimation of soil carbon sequestration in turfgrass systems using the
CENTURY model. Agron. J. 95:558–563.
Boutton, T.W. 1991. Stable carbon isotope ratios of natural materials: I. Sample
preparation and mass spectrometric analysis. p. 155–171. In D.C. Coleman
and B. Fry (ed.) Carbon isotope techniques. Academic Press, San Diego.
Bruce, J.P., M. Frome, H. Haites, H. Janzen, R. Lal, and K. Paustian. 1999.
Carbon sequestration in soils. J. Soil Water Conserv. 54:382–389.
Burt, R. (ed.). 2004. Soil survey laboratory methods manual. Soil Surv. Invest.
Rep. 42, Version 4.0. NRCS, Washington, DC.
Clay, D.E., C.G. Carlson, S.A. Clay, C. Reese, Z. Liu, J. Chang, and M.M.
Ellsbury. 2006. eoretical derivation of stable and nonisotopic approaches
for assessing soil organic carbon turnover. Agron. J. 98:443–450.
Deines, P. 1980. e isotopic composition of reduced organic carbon. p.
329–406. In P. Fritz and J.C. Fontes (ed.) Handbook of environmental
isotope geochemistry. Vol. 1. e terrestrial environment. Part A. Elsevier,
Amsterdam.
Fisher, M.J., I.M. Rao, M.A. Ayarza, C.E. Lascano, J.I. Sanz, R.J. omas, and
R.R . Vera. 1994. Carbon storage by introduced deep-rooted grasses in the
South American savannas. Nature 371:236–238.
Follett, R.F., J. Kimble, S.W. Leavitt, and E. Pruessner. 2004. Potential use of C
isotope analyses to evaluate paleoclimate. Soil Sci. 169:471–488.
Follett, R.F., E.A. Paul, S.W. Leavitt, A.D. Halvorson, D. Lyon, and G.A.
Peterson. 1997. Carbon isotope ratios of Great Plains soils in wheat–fallow
systems. Soil Sci. Soc. Am. J. 61:1068–1077.
Follett, R.F., S.E. Samson-Liebig, J.M. Kimble, E.G. Pruessner, and S.W.
Waltman. 2001. Carbon sequestration under the Conservation Reserve
Program in the historic grassland soils of the United States of America. p.
27–40. In R. Lal (ed.) S oil carbon sequestration and the greenhouse e ect.
SSSA Spec. Publ. 57. SSSA, Madison, WI.
Follett, R.F., G.A. Varvel, J.M. Kimble, and K.P. Vogel. 2009. No-till corn a er
bromegrass: E ect on soil carbon and soil aggregates. Agron. J. 101:261–268.
Golubiewski, N.E. 2006. Urbanization increases grassland carbon pools: E ects
of landscaping in Colorado’s Front Range. Ecol. Appl. 16:555–571.
Gregorich, E.G., B.H. Ellert, C.F. Drury, and B.C. Liang. 1996. Fertilization
e ects on soil organic matter turnover and corn residue C storage. Soil Sci.
Soc. Am. J. 60:472–476.
Gregorich, E.G., B.H. Ellert, and C.M. Monreal. 1995. Turnover of soil organic
matter and storage of corn residue carbon estimated from natural 13C
abundance. Can. J. Soil Sci. 75:161–167.
Lal, R., and R .F. Follett (ed.). 2009. Soil carb on sequestration and the greenhouse
e ect. SSSA Spec. Publ. 57. 2nd ed. SSSA, Madison, WI.
Milesi, C., S.W. Running, C.D. Elvidge, J.B. Dietz, B.T. Tuttle, and R.R. Nemani.
2005. Mapping and modeling the biogeochemical cycling of turf grasses in
the United States. Environ. Manage. 36:426–438.
Post, W.M., and K.C. Kwon. 2000. Soil carbon sequestration and land-use
change: Processes and potential. Global Change Biol. 6:317–327.
Qian, Y.L., and R.F. Fol lett. 2002. Assessing soil carbon sequestration in turfgrass
systems using long-term soil testing data. Agron. J. 94:930–935.
Qian, Y.L., W. Bandaranayake, W.J. Parton, B. Mecham, A.M. Harivandi, and
A.R. Mosier. 2003. Long-term e ects of clipping and nitrogen management
in turfgrass on soil carbon and nitrogen dynamics: e CENTURY model
simulation. J. Environ. ual. 32:1694–1700.
Wang, Y., R. Amundson, and X. Niu. 2000. Seasonal and altitudinal variation
in decomposition of soil organic matter inferred from radiocarbon
measurements of soil CO2 ux. Global Biogeochem. Cycles 14:199–211.
